I'iirKsltii- h'niHii nf llllmu^. I \:^ 



tlu' (•(niiiuoii red cedar. eonsHtiitiii-- the so-called ".•edar l.alls."" 

 of orann'e color, especiallv iioticeahle after ;i rain i)i tlie iiioiitli 

 of Mav. 'I'lie relation of these two forms of the flinty- us was 

 not sns[)ected until carefnily established by Oersted, a l)otanist 

 ij;ivini>' special iittentioii to such matters, and well qualified for 

 such o))servations and ex])erimeiits. The fact havin<4- ))een as- 

 certained, a thorouohly practical remedy consists in elearin<>- 

 away tlie worthless red cedars, or. in case of a few of these 

 trees, wliicli for any reason are wished to l)e saved. |)ickiu<;- oft 

 and burnin<4- the " cethir l)alls.'" In this case the spores ]))d- 

 duced on the a])])le leaves cannot germinate and <i;row on the 

 apple. l)ut must reach, 1)V wind cui'i'ents or othei'wise. the ciMlar 

 leaves, where alone one essential stai^'e of develo])ment takes 

 place. From the cedar the spores must aia,ain be carried to the 

 apple tree, or allied host, thns alternating^- liack and forth as a 

 necessary requirement of continued existence. 



This is by no means a solitary example of known alterna- 

 tions which render possible the agency of man in preventino- 

 plant diseases caused b}' these pernicious parasites: but to gain 

 the fnllest ])ossible mastery we still need much investigation 

 and experiment by those most competent to conduct them. It 

 has long been known that the rnst of wheat ( Piicc'niia f/rainl- 

 nis) has an alternate form on the barberry bush, but since the 

 rust occurs in vast regions of our country where no barberry 

 exists, we know that this plant is not positively essential to the 

 continuous development of the rust. It now seems probable 

 that the l)arberry stage is a reality, and perhaps in some way 

 beneficial to the Puccinia (rust), but not essential. It still re- 

 mains, however, to l)e ascertained whether or not there is some 

 other common plant usually found in or near the wheat fields, 

 which takes the place of the l)arberry, and thus permits the 

 continued growth of the rust. 



What might be the practical value of investigation in this 

 direction? There are annually produced in Illinois about 50.- 

 0(M),()00 bushels of wheat. The destruction of one-hundredth 

 part of the crop by this fungus probably falls, as an estimate, 

 far within the actual limits of loss as an annual average. This 

 re])resents 500,000 l)ushels, which, at seventy-tive cents ])er 

 bushel, is §87r),0()(). If it could lie demonstrated that the eradi- 



